JP2002185783A - Recorder mounted with image reader and image correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recorder with an image reader mounted thereon that reads a correction image to acquire correction data for various corrections and acquires a mean density in a correction image area at a high-speed with high accuracy and to provide an image correction method. SOLUTION: This invention provides the recorder where an image read means 106 is mounted on a carriage 101, the image read means 106 is characterized in that it has a function of integrating the output corresponding to the density of an image for a consecutive read operation time and consists of two 1st and 2nd correction means that generates corrected data in response to the integration processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus equipped with an image reading apparatus such as an image forming apparatus for correcting uneven recording density in image recording and an image correction method.

More specifically, the present invention relates to a method for determining a correction value, in particular, an image forming apparatus using an ink jet recording head having a plurality of nozzles arranged therein, and a thermal transfer recording head having a plurality of heat sensitive elements arranged therein. This is effective for an image forming apparatus.

[0003]

2. Description of the Related Art At present, as a recording method, for example, a thermal transfer method in which ink of an ink ribbon is transferred to a recording medium such as paper by thermal energy, and a flying droplet is made to adhere to a recording medium such as paper. An ink jet recording system for performing recording is known.

Among these, the ink jet recording system is widely used in printers and copiers because of its low noise, low running cost, easy downsizing of the apparatus and easy realization of colorization.

[0005] A recording apparatus using such an ink jet recording method generally uses a recording head in which a plurality of recording elements are integrated and arranged in order to improve the recording speed. The recording element includes, for example, a nozzle for discharging ink and an ink discharge port.

In such an ink jet recording apparatus, in the case of the serial scanning system in which the recording head scans in the main scanning direction, one of the factors of image quality deterioration is recording unevenness (hereinafter referred to as streaking) which appears in the main scanning direction. , "Sujimura").

[0007] The stripes often appear periodically,
In that case it is very noticeable. For example, in a so-called multi-nozzle type recording head in which a plurality of ink ejection ports are provided, in order to eject ink from each ejection port, a heating heater (electrical heater) located in an ink flow path communicating with each ejection port. In the case of using the heat generated by the heat converter, the following causes of unevenness can be cited. That is, variations in the ejection amount and ejection direction of the ink due to variations in the size of the heating heater and the ejection port in the nozzle unit during manufacturing, the transport amount (paper feed amount) of the recording medium in the case of the serial scan method, and recording. The deviation from the width, the difference in the change in the density of the ink caused by the deviation in the recording time, the movement of the ink on the recording medium, and the like cause the occurrence of the stripes.

Hitherto, various methods have been proposed for eliminating such unevenness and improving the image quality.

As one of the methods, there is a division printing method (multi-pass printing method) for completing printing in one printing area on a printing medium by scanning the printing head a plurality of times. Such a divided recording method is very effective for eliminating streaks and unevenness.

However, in order to sufficiently enhance the effect, the number of scans of the print head for one print area, that is, the number of divisions must be increased, and one print head is required.
The recording area completed each time the scanning is performed becomes small, and the throughput is reduced.

As another method for suppressing the occurrence of line unevenness without using such a divided recording method, there is, for example, a head shading method as described in Japanese Patent Application Laid-Open No. 5-69545. This method is performed in the order shown in FIG.

First, a preset test pattern for determining a correction value is recorded on a recording medium using a recording head (step S11), and the recording density of the recorded test pattern is read by a scanner (step S1).
2). After appropriately correcting the position of the read image, the density of the image is averaged in the column direction (main scanning direction) (step S13), and is assigned to a raster corresponding to each nozzle of the recording head (step S14). The change in the recording density is caused by a shift in the ink ejection amount or ejection direction for each nozzle, or bleeding of the ink on the recording medium. In the next step S15, a correction value of the recording density for each nozzle is calculated and determined from the density data assigned to each raster in step S14.

The image data for each nozzle is corrected based on the correction value (step S16).

Specifically, the gamma table for each nozzle is changed, or the drive table for each nozzle is changed to change the ink discharge amount and the like. By the correction of the image data based on such a correction value, a raster recorded densely in a state without correction is corrected so as to be thin, and a raster recorded thinly in a state without correction is corrected. It is corrected so that it becomes dark, and the unevenness of the recording density is reduced. In particular, a method of changing the output γ table for each nozzle and changing the original density of the original image data to correct the density is extremely effective for correcting uneven recording density.

Further, JP-A-5-69545 discloses that
A method for recording an image without streaks or unevenness at all gradation levels by not correcting the low-density recording area but correcting the high-density recording area in consideration of the input gradation is also described. ing.

Another factor in lowering the image quality is a problem in forming an image using a plurality of heads.
Specifically, in a printing apparatus having a plurality of heads, there is a problem in a case where the landing positions of dots are misaligned among a plurality of heads.

When performing image printing, an image is often formed by combining several types of colors. The most common method is to use four colors obtained by adding black to the three primary colors of yellow, magenta and cyan. General. When a plurality of print heads for printing these colors are used, if there is a deviation in the landing position between the print heads, a color shift occurs when different colors are printed on the same pixel depending on the amount of displacement. Would. For example, magenta and cyan are used to form a blue image, but when the dots of both colors overlap, they become blue, but where they do not, they do not become blue and each color appears independently. Color shift. Even if this occurs partially, it does not stand out, but if this phenomenon occurs continuously in the scanning direction, a band-like color shift of a specific width results in an uneven image. Furthermore, if there is no deviation in the landing position of the dot in an area adjacent to the image of the same color, the uniformity and color development are different between the adjacent image areas, and the image is uncomfortable. Further, this color shift is not so noticeable on plain paper, but may be noticeable when using a recording medium with good coloring such as coated paper.

Further, when printing different colors on adjacent pixels, if there is a deviation in the landing position of the dot, a gap, that is, an area that is not covered by ink is generated in that part, and the ground of the recording medium is directly visible. Sometimes. This phenomenon is often referred to as "white spots" since recording media generally have a white background. This phenomenon is conspicuous in images with strong contrast, and in the case of forming a black image with a chromatic color as a background, a white gap without ink exists between black and the chromatic color. The contrast between them is so strong that they may be more noticeable.

In order to suppress the above problems from occurring, it is effective to perform the above-described dot alignment.
This method is specifically described in Japanese Patent Application Laid-Open
No. 291553.

Further, in that document, a bidirectional printing method is described as a technique for speeding up printing. Specifically, in a print head having a plurality of print elements, it is considered to increase the number of print elements and to improve the scanning speed of the print head, but it is also possible to perform reciprocal print scanning of the print head. One effective method. In a printing apparatus, since there is usually time for paper feeding and paper discharging, a simple proportional relationship is not obtained, but bidirectional printing can obtain a printing speed about twice as fast as one-way printing.

However, the following problems are caused in bidirectional printing.

First, when printing a ruled line (vertical ruled line) in the direction perpendicular to the main scanning direction of the print head, the ruled line printed on the forward path and the ruled line printed on the return path do not align with each other, and the ruled line is straight. Instead, a step occurs.
This is what is called "ruled line displacement",
It can be said that this is the most general image disturbance recognized by a general user. Since ruled lines are often formed in black,
Although generally recognized as a problem in forming a monochrome image, a similar phenomenon occurs in a color image.

Further, when multi-scan printing is used in combination for high image quality, even if the landing positions do not match in bi-directional printing, the shift at the pixel level is not so noticeable as an effect of multi-scan printing, but is macroscopic. , The entire image looks uneven, and some users may recognize it as an unpleasant pattern. Although this is generally called texture, it occurs when a slight displacement of the landing position appears on the image in a specific cycle. It may be conspicuous in an image having a strong contrast such as a monochrome image, and may be conspicuous when performing halftone printing on a recording medium or the like capable of high density printing such as coated paper.

As described above, JP-A-11-2915
Japanese Patent Application Laid-Open No. 53-53605 provides a print position alignment method that is simple and accurate with respect to print position alignment between reciprocating scans of a print head in a printing apparatus and print position alignment method between a plurality of print heads.

The method will be briefly described. In reciprocal scanning of a head or complementary printing by a plurality of heads, a print start timing is set with respect to a reference dot (forward scan or a dot formed by one of the heads). Print multiple patterns shifted by a fixed amount. In these patterns, it is assumed that the area factor of the dots formed by the printing changes according to the shift. The plurality of patterns are optically read as an average density.

The timing corresponding to the portion having the highest read average density is set as the print alignment condition.

[0027]

In the above-described conventional example, the above-described correction operation is performed automatically and accurately in the recording apparatus, which is very effective for the user. However, in the above conventional example, a step of recording a correction image to obtain data for performing the correction and reading the density of the recorded image is always required.

Here, when a large number of correction images need to be read, a lot of time is required for the reading operation, and there is a problem that the overall adjustment time is prolonged.

On the other hand, in reading the image density, the correction image to be read has a certain finite area, and it is rare that the density is uniform in all the areas. Further, when the image is viewed microscopically, since the image is entirely formed of a single dot, it is necessary to acquire average data in a finite area in principle when reading the image density. Conventionally, as a method for improving the accuracy of the read data, a method of performing a read operation from the same image area a plurality of times while changing the reading location within the area and averaging a plurality of obtained image density data has been adopted. Had been. In this case, since the actual reading operation is performed much more times than the number of correction images to be read, the reading operation (acquisition of the average image density) takes more time. .

The present invention has been made in view of the above circumstances, and in reading a correction image for obtaining correction data for performing various corrections, the average density in the correction image area is increased at a high speed. It is another object of the present invention to provide a recording apparatus equipped with an image reading apparatus capable of acquiring images with high accuracy and an image correction method.

[0031]

The present invention can solve the above-mentioned problems by providing the following constitution.

(1) A recording apparatus having image reading means mounted on a carriage, wherein the image reading means has a function of integrating output corresponding to image density during continuous reading operation time, A recording apparatus equipped with an image reading apparatus, comprising: first and second two correction means for generating data for correcting an image in accordance with an integration process.

(2) The first correction means has a function of correcting an image from the image data read by the image reading means, and is obtained by reading the image data in accordance with the characteristics of a recording head mounted on a recording apparatus. A recording apparatus equipped with the image reading apparatus according to the above (1), wherein the density unevenness of the original image data is corrected based on the obtained image data.

(3) The second correction means has a function of correcting an image from the image data read by the image reading means, and is obtained by reading the image data according to the characteristics of the recording head mounted on the recording apparatus. (1) wherein the recording position of the image data is corrected based on the image data obtained
A recording device equipped with the image reading device described in the above.

(4) A recording device equipped with the image reading device according to (1), wherein the image reading means is a CCD image sensor.

(5) A recording device equipped with the image reading device according to (1), wherein the image reading means is a MOS image sensor.

(6) The image reading means is a CMOS
A recording device equipped with the image reading device according to the above (1), which is an image sensor.

(7) An image correction method for a recording apparatus in which image reading means is mounted on a carriage, wherein the image reading means has a function of integrating an output corresponding to an image density during a continuous reading operation time. The image processing apparatus further includes first and second correction means for generating data for correcting an image in accordance with the integration processing, and the image reading means reads the data according to the characteristics of a recording head mounted on the recording apparatus. Correcting the density unevenness of the original image data based on the image data obtained by the image reading device, and performing image formation based on the image data obtained by reading by the image reading means in accordance with the characteristics of the recording head mounted on the recording device. Correcting the data recording position.

That is, in order to solve the problem, a function of integrating an output corresponding to the density of an image during a continuous reading operation time is added to the image reading means, and the image reading means further includes a function of determining a predetermined image for correction. By performing scan processing during the continuous reading operation in the area of, the average density in the correction image area (strictly speaking, it is an integrated density, and if the average density is necessary, it can be obtained by dividing by the scan time. , And the scanning time is kept constant to obtain an equivalent average density).

As a result, density data in the correction image area can be continuously taken in, and the data can be obtained with higher precision and higher speed than the conventional average value of sampling data of a plurality of points. Things.

[0041]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic explanatory view showing a configuration of a recording apparatus according to the present invention, FIG. 2 is an explanatory view showing an essential configuration of a reading unit in the recording apparatus according to the present invention, and FIG. FIG. 4 is an explanatory diagram showing a method of reading average density data of a correction image according to a method, FIG. 4 is an explanatory diagram showing a method of reading average density data of a correction image according to the present invention, and FIG. 5 is a conventional correction value determination method. It is a flowchart.

In FIG. 1, reference numeral 101 denotes a carriage for mounting an image recording head.
A plurality of image recording heads 102, 10 having separate housings on one
3, 104 and 105 are mounted. The plurality of different image recording heads are, for example, heads for recording a plurality of colors when recording a color image (a head for recording a black image, a head for recording a yellow image, a head for recording a magenta image, a head for recording a cyan image, and the like). ). The carriage 101 is provided with image reading means 106 for reading an image recorded on the recording medium 114.

The carriage 101 on which the image recording heads 102 to 105 are mounted reciprocates left and right (main scanning direction) with a guide rail 110 as a guide by a belt 109 supported by a pulley 108 using a motor 107 as a driving source. It has become. Thus, the image reading means 106 can be moved in the main scanning direction with respect to the recording medium 114.

The gear 1 is driven by using the motor 112 as a drive source.
The recording medium 114 is conveyed in the up-down direction (sub-scanning direction) by the conveying roller 111 rotating through the recording medium 114. Thus, the image reading unit 106 can be moved in the sub-scanning direction with respect to the recording medium 114.

In FIG. 2, reference numeral 201 denotes an image reading means, which in this embodiment is an optical reflection type image sensor. This sensor has a light emitting unit 202 and a light receiving unit 203 inside.
And a light emitting unit 2 for a correction image 206 serving as a test pattern for various image correction and recording position correction recorded on the recording medium 205 by the light emitting unit 203.
Light is emitted from the light receiving portion 203 and the light receiving portion 203 receives a reflected light amount corresponding to the image density.

Accordingly, in the light receiving section 203, an output corresponding to the image density is generated at the light receiving section 203, and the output is time-integrated by the integrating section 204, and finally this integrated output is output from the image reading section 201. It has a configuration.

Next, a method for reading average density data of a correction image and a method for reading average density data of a correction image according to the present invention will be described with reference to FIGS.

In FIG. 3, conventionally, in order to obtain the average density of the correction image, the reading sensor is moved to positions indicated by a to o in FIG. 3, the sensor output at each position is read, and the average value is calculated. The average density data of the image for correction was read by obtaining it. In this case, an error occurs in the average density unless more sample data is taken while shifting the reading position finely, so that much time is spent on reading and averaging the read data.

On the other hand, FIG. 4 shows a reading method according to the present invention. Since the reading sensor itself is provided with an integrating means, the output is output while scanning the sensor from A to B in FIG. By successively integrating, it is possible to obtain the sum of outputs according to the continuous density between A and B. If the average density is required, it can be obtained by dividing by the scan time. In most cases, the relative comparison of the image density for correction is performed. It is possible to handle.
As described above, it is possible to continuously scan the inside of the correction image area and obtain the density, so that it is possible to obtain data closer to the original average density of the correction image in one reading operation. Become.

In the embodiment according to the present invention shown in FIG. 4, a case where the correction image area is scanned in a straight line is shown.
Needless to say, the left side can arbitrarily scan the inside of the correction image area by combining the main scanning and the sub-scanning in FIG.

Further, as the reading means of the present invention, specifically, a CCD image sensor, a MOS image sensor, or a CMOS image sensor has a function of accumulating (integrating) electric charges converted photoelectrically in the sensor. Therefore, it can be said that this is the most suitable sensor, but it can also be realized by integrating the output of a normal photosensor with an analog integrator.

[0053]

As described above, according to the present invention, density data in a correction image area can be continuously taken in, and can be obtained with higher precision than a conventional average value obtained by sampling data at a plurality of points. And the data can be obtained at high speed. Therefore, in various image corrections and recording position corrections, the time required for the adjustment can be shortened, and the adjustment accuracy can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing the configuration of a recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a main configuration of a reading unit in the recording apparatus according to the present invention.

FIG. 3 is an explanatory diagram showing a method of reading average density data of a correction image according to a conventional method.

FIG. 4 is an explanatory diagram showing a method for reading average density data of a correction image according to the present invention.

FIG. 5 is a flowchart showing a conventional correction value determination method.

[Explanation of symbols]

 101 carriage 102, 103, 104, 105 image recording head 106, 201 image reading means 107 motor 108 pulley 109 belt 110 guide rail 111 transport roller 112 motor 113 gear 114, 205 image recording medium 202 light emitting section 203 light receiving section 204 integrating section 206 Correction image (test pattern)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H04N 1/407 H04N 1/40 101E F-term (Reference) 2C056 EA04 EB27 EB42 EC07 EC37 EC42 EC75 EC79 FA10 HA58 2C066 AA03 BC03 BC04 BC16 CZ05 5C072 AA05 BA03 BA04 EA05 EA06 KA01 MA01 QA14 RA18 SA04 UA01 XA04 5C074 AA09 AA10 BB16 CC03 CC25 CC26 DD01 EE04 FF15 GG01 GG19 5C077 LL04 LL11 LL18 PP19 MM03 PP04

Claims (7)

[Claims] 1. A recording apparatus in which image reading means is mounted on a carriage, wherein said image reading means has a function of integrating an output corresponding to an image density during a continuous reading operation time. A recording apparatus equipped with an image reading apparatus, comprising: first and second correction means for generating data for correcting an image according to processing. 2. The image processing apparatus according to claim 1, wherein the first correction unit has a function of correcting an image from the image data read by the image reading unit, and the first correction unit obtains the image by reading the image data according to characteristics of a recording head mounted on a recording apparatus. 2. A recording apparatus equipped with the image reading apparatus according to claim 1, wherein the density unevenness of the original image data is corrected based on the image data. 3. A second correction unit having a function of correcting an image from image data read by the image reading unit, and obtained by reading the image data according to characteristics of a recording head mounted on a recording apparatus. 2. A recording apparatus equipped with the image reading apparatus according to claim 1, wherein a recording position of the image data is corrected based on the image data. 4. The recording apparatus according to claim 1, wherein said image reading means is a CCD image sensor. 5. The recording apparatus according to claim 1, wherein said image reading means is a MOS image sensor. 6. The recording apparatus according to claim 1, wherein said image reading means is a CMOS image sensor. 7. An image correction method for a recording apparatus in which image reading means is mounted on a carriage, wherein said image reading means has a function of integrating an output corresponding to an image density during a continuous reading operation time. First and second correction means for generating data for correcting an image in accordance with the integration processing, wherein the image data is read by the image reading means in accordance with the characteristics of the recording head mounted on the recording apparatus. Correcting density unevenness of the original image data based on the obtained image data; and image data based on the image data read by the image reading means in accordance with the characteristics of the recording head mounted on the recording apparatus. Correcting the recording position of the image.